VARIABILITY IN MACRONUTRIENT COMPOSITION OF WEED SEEDS

The analysis of the element composition of weed seeds and shoots could provide new data for their biological and ecological assessment. In the present study, seed samples of 30 weed species from different plant families were analysed for macronutrients (K, Ca, Mg, N, P, S) and high variability was found. There was a considerable difference in the N content of weed seeds, with the highest value for Asclepias syriaca and the lowest for Xanthium spinosum. The macroelement ratio also exhibited a wide range of values, e.g. the N to S ratio varied from 0.2 to 14.2. When crop seed data were compared to those of weed seeds from the same family, the K, Ca, Mg, P and S concentrations in weed seeds were found to be significantly higher in many cases. There were significant differences both in the macroelement concentrations and, in some cases, in the nutrient ratios of weed seeds from different plant families. Significant differences were found for K, Mg, P and S, and for the N/S and Ca/P ratios. This was confirmed by PCA, which illustrated not only differences between weed species, but also the fact that weed plants from the same family formed groups.